There are food processors of the type broadly set forth above having a working bowl or vessel with a motor driven shaft projecting vertically upwards through the bottom of the bowl on which various selected rotary tools can be engaged to be driven by the shaft for performing various food processing operations as may be desired by the user. A detachable cover is secured over the top of the bowl during use. This cover includes a hopper or feed tube which has a mouth that opens downwardly through the cover into the top of the bowl. The food items to be prepared are placed in this feed tube and then are manually pushed down through the feed tube into the bowl by means of a removable pusher member which is adapted to slide down in the manner of a plunger into this feed tube. For further information about this type of food preparing apparatus, the reader may refer to U.S. Pats. Nos. 3,985,304-Sontheimer and 4,216,917-Clare et al, 4,198,887-Williams, and 4,227,655-Williams.
The rotary tools in food processors are being driven by relatively powerful motor drive arrangements and have the capability of causing injury. For this reason, a bowl-cover safety feature is conventionally incorporated into these units. This feature requires that the cover be firmly locked onto the bowl in normal position before the motor will start. This requirement is achieved by making the cover, which locks rotationally to the bowl, with a projection or member which causes the closing of a switch carried in the housing only when the cover is properly locked into its normal position on the bowl. Depending upon the type of food processor, this cover projection may actuate the switch directly or through an intermediate linkage.
U.S. patent application Ser. No. 155,200, filed June 2, 1980, by Sontheimer et al entitled "Magnetic Safety Interlock Method and Apparatus for Food Processor" discloses a safety interlock in which the motor drive can only be actuated by an appropriately coded magnet. The embodiment disclosed in FIGS. 13-17 of the patent application illustrate the use of two striped permanent magnets both of which are orientated in a horizontal direction with respect to the base housing. Each of the magnets comprises adjacent magnetic stripes of alternating magnetic polarity which extend widthwise across the respective magnets.